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Fabrication of Curie point written solid state magnetic memories

居里点写入固态磁存储器的制作

基本信息

批准号：
13555092
负责人：
TSUNASHIMA Shigeru
金额：
$ 8.7万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13555092/
关键词：
solid state magnetic momery MRAM spin tunneling junction non-volatile memory Blocking temperature exchanae anisotropy spin polarized transport

项目摘要

Micropatterned amorphous films for thermomagnetic recording, TMR films using amorphous alloy layers, exchange biased films, and thermomagnetic recording process were investigated.(1) TbFe amorphous alloy films were prepared by rf magnetron sputtering, and microfabricated by focused ion beam (FIB) and conventional photolithography methods. Switching of the magnetization of TbFe elements was confirmed after current pulses which give rise to Joule heat in the elements. The current density necessary for the switching was found to decrease with decreasing the element size, and the 0.5μm squared element was found to be switched by applying the current density as small as 1.6 x 10^6 A/cm^2. In addition, tunnel junctions including TbFe amorphous alloy layer was found to exhibit sufficiently large magneto resistance ratio.(2) NiFe/Mnlr exchange biased films were microfabricated by FIB and their magnetic domain structures were observed by magnetic force microscopy (MFM). The easy direction of the NiFe/Mnlr elements lay in the film plane, and for such in-plane elements having 1 : 1 aspect ratio, it is difficult to obtain sigle domain state. Thus, the perpendicular magnetized elements such as TbFe were found to be effective to accomplish single domain state if the elements have 1 : 1 aspect ratio.(3) Simulation of thermomagnetic recording process was carried out, and the simulation was used to obtain material parameters which are necessary for recording of domains smaller than 100 nm. For the recording of domains smaller than 50 nm on an RE-rich TbFeCo medium, the increase of coercivity, which might be realized by controlling the microstructure of the TbFeCo film, was found to be needed.

研究了用于热磁记录的微图案化非晶薄膜、使用非晶合金层的TMR薄膜、交换偏置薄膜以及热磁记录工艺。(1)采用射频磁控溅射法制备了TbFe非晶合金薄膜，并采用聚焦离子束（FIB）和传统光刻技术对薄膜进行了微加工。TbFe元件的磁化的切换被确认后，电流脉冲引起焦耳热的元素。发现开关所需的电流密度随着元件尺寸的减小而减小，并且发现通过施加小至1.6 x 10^6 A/cm^2的电流密度，0.5μm平方的元件被开关。此外，发现包括TbFe非晶合金层的隧道结表现出足够大的磁阻比。(2)采用FIB技术制备了NiFe/Mnlr交换偏置薄膜，并利用磁力显微镜（MFM）观察了薄膜的磁畴结构。NiFe/Mnlr元素的易磁化方向位于薄膜平面内，对于具有1：1纵横比的面内元素，很难获得单畴态。因此，垂直磁化的元素，如TbFe被发现是有效的，以实现单畴状态，如果元素具有1：1的纵横比。(3)对热磁记录过程进行了模拟，并利用模拟得到了记录小于100 nm磁畴所需的材料参数。对于记录小于50 nm的域上的稀土丰富的TbFeCo介质，增加的结晶度，这可能是通过控制的TbFeCo膜的微结构实现的，被发现是必要的。